The present invention relates to a gas inflator for an airbag on a motor vehicle steering wheel. In particular, the present invention relates to a gas inflator which reduces vibrations in a steering column.
In motor vehicles, vibrations arising during driving or even during idling can be transmitted to the steering column and from there to the steering wheel. To counteract these vibrations in the steering wheel and to improve driving comfort, vibration dampers have been installed either directly on the steering column or in the steering wheel beneath the airbag module located there. More recent solutions use the airbag module or the gas inflator of the airbag module as a vibration damper.
From German Published Patent Application 39 25 761, by way of example, a design is known in which either the airbag module or a part of it, in this case, the gas inflator, is used as the inertial mass. In the event that the gas inflator is the inertial mass, the gas inflator is surrounded by a netlike encasement, which prevents the airbag and the gas inflator from coming into contact with each other. The airbag could be damaged in this way and the mobility of the gas inflator could be impaired. In one configuration of this type of airbag and gas inflator, a self-activation of the gas inflator is possible because the latter can vibrate at high rates of acceleration. It is also disadvantageous that the chosen connecting means between the gas inflator and the airbag, bolts or rivets having elastic sleeves, only permit small vibration amplitudes. The deformation capacity of the elastic means employed is sharply limited by the connecting means themselves (rivets, bolts).
Another solution, disclosed in the German Design Patent 299 02 033, is made up of an annular metal mounting plate arranged on the gas inflator support, a circumferential mounting flange connected to the housing of the gas inflator, and a mounting cylinder, made of an elastic material and oriented parallel to the steering axis. The free edges of the mounting cylinder are connected, on the one hand, to the mounting metal plate and, on the other hand, to the mounting flange. In this manner, only the gas inflator is connected to the remaining components of the airbag module via the mounting cylinder made of an elastic material. As a result of the design shape and the material selection, the mounting cylinder can be adjusted to varying requirements, so that the vibrations, varying from vehicle type to vehicle type, can be effectively suppressed. Although this solution provides a very effective vibration damping, the explosive and the other components of the gas inflator can be destroyed by excessive accelerations (impacts). This is especially the case when a spacer pot is provided between the gas inflator and airbag for the protection of the airbag, and the gas inflator strikes against the wall of the spacer pot. Furthermore, the noise generated by the gas inflator striking against the wall of the spacer pot is annoying.
The present invention is based on the objective of finding a design configuration for the airbag module in which the aforementioned disadvantages are avoided. In accordance with this objective, a gas inflator for an airbag is movably mounted in a spacer pot and/or protective sleeve of an airbag housing by annular spring element made of a polymer material. The annular spring element is impermeable to gas, and is connected to the gas inflators"" outer wall, and to a supporting plate. A vacant space is formed between the gas inflator and the interior wall of the spacer pot or protective sleeve, and the gas inflator functions as an inertial mass. The annular spring element has a plurality of elastic projection distributed on its exterior periphery. The elastic projections dampen impacts by causing a defined deceleration of the gas generator in response to the transversing of the vacant space. In this manner, damage to the gas inflator or to parts of gas inflator is prevented.
The spring element is configured as a sleeve-shaped truncated cone open at the top. This configuration of the spring element yields production-technical advantages in vulcanizing and counteracts the vibrating motions of the gas inflator in the radial direction.
Preferably, the projections are arranged on the part of the spring element that is connected to the gas inflator. The connection between the gas inflator and the spring element is preferably effected by an interior ring, which is pressed, in a force fit, onto the exterior wall of the gas inflator. The ring is connected by vulcanization to the spring element. It is expedient if the ring extends over the entire height of the projections. Of course, it is also possible to connect the ring to the exterior wall of the generator, the wall being configured in a form-locking manner. To make it easier to install the ring on the exterior wall of the gas inflator, the ring at its upper edge is slightly flattened down. In this manner, a funnel-like rounding-off is produced which makes the mounting of the ring easier. Other design solutions are possible here without moving away from the inventive idea.
The end of the spring element that is connected to the supporting plate is vulcanized to the supporting plate. In this context, it is expedient if the end of the spring element surrounds the edge of the supporting plate in a bead-like manner.
By shaping the projections, a defined spring rate can be preestablished. In this way, the projections can each have at least one lip-shaped or truncated-cone-shaped protuberance. The smaller the contact surface between the protuberance and the spacer pot, the greater the spring rate and vice versa. The projections also prevent a smacking noise from arising from surface contact between the spring element and the spacer pot.